The present invention relates to methods of and apparatus for extracting samples of a dry material product from a main body of product in a tank or vessel.
Various manufacturing operations require that the immediate or overall composition of a product be monitored. Such monitoring may be accomplished with samplers for taking samples of the product from a main body of the product. When a composite sample is required, the sampler may be periodically operated to withdraw small samples of product from the main body, which samples are mixed together and represent a composite of the main body of product. Other uses for samplers are in applications in which the immediate composition of a product must be determined. In this case, the samples are individually analyzed.
To obtain samples of a dry material product, some samplers divert material from the main body of product and from the diverted material samples are removed in various ways. Attempts to withdraw small samples of a dry product directly from a main body of product, however, have presented many problems not altogether satisfactorily solved. For example, where product receiving holes or slots in a sampler are extended directly into a vessel, sampled product can build up in such holes and slots and either block the same or contaminate subsequent samples.
Other samplers utilize a plunger that is extended through a sampler body bore into a main body of product to receive a sample of product in a sample-receiving opening in the plunger. The plunger is then retracted to convey the sample to a collection point. Four samplers of this type are disclosed in U.S. Pat. Nos. 4,147,062, 4,262,533, 4,475,410 and 4,744,255, issued to the present inventor and the teachings of all of which are incorporated herein by reference. These samplers are primarily adapted to sample liquid products, and are attached to an access line to a vessel containing liquid product to be sampled, so that a sample-receiving opening in a plunger of the sampler can be extended into the product in the vessel to obtain a sample of product. The plunger is then retracted to deliver the sample to a collection point.
When a plunger-type sampler is idle, its plunger normally is refracted and the front of the plunger is rearward from a forward opening from the sampler bore. The forward end of the bore, between the front of the plunger and the opening, is then exposed to and can fill with product from the vessel. If the sampler is idle sufficiently long, product from the vessel may fill, coalesce in and block the sampler bore in front of the plunger. The blockage can then disable the sampler by preventing subsequent reciprocation of the plunger to obtain samples.
U.S. Pat. No. 6,164,145, issued to the present inventor and the teachings of which are incorporated herein by reference, addresses the problem of product collecting in and clogging a forward end of a sampler bore in front of a plunger when the sampler is idle. According to this patent, when a sampler is to be idle, the sampling plunger is moved to a parked position in the sampler bore, where the forward end of the plunger is very close to or at the forward opening from the bore. The plunger then serves to close the opening to the bore, so that product in the vessel cannot enter and collect in the bore in front of the plunger. This technique prevents potential contamination of subsequent samples and ensures that the sampler is not rendered inoperative by product clogging the front of the bore.
The sampler of said U.S. Pat. No. 6,164,145 is advantageous for use with liquid products that tend collect in and to block a sampler bore, such as a product comprising paper pulp, but it is not well adapted for sampling a dry material product. Such a dry product could comprise, for example, a dry food product comprising various dry ingredients that are separately introduced into and mixed in a blender. In the case of such a product, it often is desirable at to obtain samples of the product various stages of mixing to determine the extent to which the individual ingredients have been mixed together and when the product has been fully and properly blended. The prior art does not provide a plunger-type sampler that is suitable for sampling such a dry material product.
An object of the present invention is to provide a sampler that is adapted to sample a dry material product.
Another object of the present invention is to provide such a sampler of the reciprocating plunger type.
A further object is to provide such a sampler that, when idle, cannot be disabled by product entering and blocking a sampler bore within which the plunger is reciprocated.
Yet another object is to provide such a sampler in which the length of the sampler bore forward from the plunger is minimized when the sampler is idle.
A still further object is to provide such a sampler in which the plunger is at a first position in the sampler bore when delivering a product sample at a sample collection point in the bore, is at a second position in the bore when the sampler is idle, and is at a third position in the bore when obtaining a product sample.
In accordance with the present invention, a sampling apparatus comprises a sampler that is operable to obtain discrete samples of a dry material product from a main body of product. The sampler includes a sampler body having a bore with a forward opening, and plunger means having a product sample receiving opening is in the bore. Means are provided to reciprocate the plunger means in the bore to a sample receiving position where the plunger means sample receiving opening is extended forward out of the forward bore opening, to a sample delivering position where the plunger means sample receiving opening is retracted rearward to a sample collecting point in the bore, and to a parked position in the bore intermediate the sample receiving and delivering positions where the plunger means closes the forward opening from the bore. In addition, included is means for locking and unlocking the plunger means against and for reciprocation when the plunger means is in the parked position.
In the described embodiment of sampling apparatus, the plunger means has a forward end that is positioned rearward from the forward opening from the bore when the plunger means is in the sample delivering position, and that is positioned close to and preferably at the forward opening when the plunger means is in the parked position. The plunger means sample receiving opening comprises an annular recess in and circumferentially around the plunger means, and the plunger means and the means for reciprocating are connected for conjoint reciprocation. The means for locking and unlocking the plunger means locks and unlocks the means for reciprocating against and for reciprocation when the plunger means is in the parked position.
The means for reciprocating the plunger means is manually actuated and includes a handle for being moved by an operator and a driver rod connected at one end to the handle and at an opposite end to the plunger means. Means are provided for guiding and controlling the extent of reciprocation of the handle, driver rod and plunger means, which means includes a guide sleeve around the driver rod, a longitudinal slot in the guide sleeve and a stop carried by the driver rod and extending into the slot. The stop reciprocates in the slot with reciprocation of the driver rod in the guide sleeve, so that the slot guides the stop, handle, driver rod and plunger means during reciprocation. The slot has forward and rearward ends that are engaged by the stop to limit the extent of forward and rearward reciprocation of the plunger means.
The means for locking and unlocking the plunger means against and for reciprocation includes means for locking and unlocking the stop against and for reciprocation in the guide sleeve slot when the plunger means is in the parked position. Such means for locking and unlocking includes a circumferential extension of the slot that extends generally perpendicular to the longitudinal extent of the slot. The stop is moved into the circumferential slot extension when the plunger means is in the parked position to lock the stop and thereby the plunger means against reciprocation, and the stop is moved out of the circumferential slot extension to unlock the plunger means for reciprocation. The handle, drive rod, stop and plunger means are conjointly rotated when the plunger means is in the parked position to move the stop into and out of the circumferential extension.
The invention also contemplates a method of obtaining samples of a dry material product, which comprises the steps of providing a sampler body having a longitudinal bore and a forward opening from the bore, and positioning in the bore a plunger having a sample receiving recess intermediate forward and rearward ends of the plunger. Included are the steps of extending the plunger forward through the bore to a plunger sample receiving position where the forward end and recess of the plunger are projected out of the bore opening into a body of dry product to receive in the recess a sample of product, then retracting the plunger rearward through the bore opening to a plunger sample delivering position to convey the product sample in the recess to a sample collecting point, and then removing the sample from the plunger recess at the sample collecting point. When the plunger is at the sample delivering position, its forward end is spaced rearward from the bore opening, so that a length of open bore then exists between the plunger forward end and the opening from the bore, into which product from the body of product can enter and accumulate. To prevent product from entering and stagnating in the length of open bore and potentially clogging the bore, after performance of the step of removing the product sample from the plunger recess, included is the step of moving the plunger forward to a parked position, intermediate the sample delivering and receiving positions, where the forward end of the plunger closes the opening to the bore. The step is then performed of locking the plunger in the parked position.
The step of moving the plunger to the parked position comprises moving the plunger to position its forward end close to and preferably at the bore opening, so that the plunger forward end then closes the bore and prevents entry into the bore of dry product from the body of dry product Each of the plunger extending, retracting and moving steps is manually performed.
The foregoing and other objects, advantages and features of the invention will become apparent upon a consideration of the following detailed description, when taken in conjunction with the accompanying drawings.